The above noted U.S. Pat. No. 3,822,327 discloses the preparation of homopolycondensed vinylphosphonates, the neutralization of the resulting homopolycondensates with epoxide reagents and the use of these neutralized homopolycondensates for preparing flame retardant textile finishes. The copending applications discose copolycondensed vinylphosphonates which are prepared by the co-condensation of particular phosphonates with particular pentavalent phosphorus esters as hereinafter described.